Fluid pressure servomotor



United States Patent C) 3,289,547 FLUID PRESSURE SERVOMOTOR Oswald O. Kytta, South Bend, Ind., assignor to The Bendix Corporation, South Bend, Ind., a corporation of Delaware Filed Dec. 14, 1964, Ser. No. 417,941 Claims. (Cl. 91-376) The present invention relates to a fluid pressure servomotor, and m-ore particularly to a novel construction for a plurality of movable walls within the servomotor, including novel means for retaining a control valve mechanism in one of the movable rwalls. i

An object of the present invention is the provision of a simplified construction for uniting a pair of movable walls within a uid pressure servomotor in such a manner as to provide fluid passage means between chambers thereof, and at the same time retain internal parts in an operative position within one of the movable walls.

A further object of the present invention is the provision of a new and improved construction of movable walls for a tandem type fluid :pressure servomotor in` which 'one of the movable walls has an axially extending valve chamber that is axially open, and into which various valve elements Iare placed and held therewithin by the attachment of another movable wall to the one movable wall having the valve chamber as by threading the oth-er movable wall thereto. The other movable wall is to provide a fluid passage means for chambers within the fluid pressure servomotor and operatively c-onnects a reaction means to the valve elements to provide an operator of the servomotor with a proportional feel.

The invention resides in certain constructions and combinations and arrangement 1of parts; .and further objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiment described with reference to the accompanying drawings forming a part of the specification, :and in which:

FIGURE 1 is a cross sectional view of a fluid pressure servomotor embodying principles of the present invention; and

FIGURE 2 is an exploded view of the valve element details as seen in FIGURE 1.

With more particular reference to FIGURE l, I show a fluid pressure ,servomotor having a housing assembled from a front shell portion 12 and a rear shell portion 14 united by aligning notches within the portion 12 with the .radially inwardly bent portions 16 of shell portion 14 and twisting the shell 12 until the ears 18 are locked behind the inwardly bent portions 16.

However, before assembling the housing, movable walls 20 and 22 are positioned within the portion 14 by means of an annular diaphragm retainer 24 and a plastic spacer 26 provided with a serrated edge 28. As seen, the spacer is interposed between the front diaphragm 30 and the diaphragm retainer 24 which are compressed against the radially outwardly extending ears 18 .and a shoulder 32 of the front shell portion 12 and the rear shell portion 14, respectively.

The diaphragm retainer 24 is constructed with an axially extending member having rearwardly depending projections 34 formed with notches therebetween to provide a plurality of continuous and spaced spring fingers. The body of the retainer 24 is also provided with an edge opposite the depending projections which is to abut a stepped shoulder 36 of the spacer 26 and overlie a rear diaphragm 38 having a periphera'ly thickened portion with a groove therein to receive Ia lip 40 of the spacer 26 with a forward edge of the radially thickened portions abutting the lower extremity of the stepped shoulder 36 and being ICC compressed onto the lip 40 by the diaphragm retainer 24. Such compression can be easily accomplished by providing a bulbous radial projection adjacent the forward edge on the thickened portion immediately under the retainer 24 that is compressed by sliding the retainer 24 over the bulbous portion until it abuts the spacer stepped shoulder 36.

Both the front diaphragm 30 and rear diaphragm 38 having the peripherally thickened bead `41 are provided with central openings and beads 44 .and 42, respectively, therearound which are undersize with respect to grooves 48 and 46 in movable walls 20 and 22, respectively, to provide an interference lit therebetween and thereby divide the servomotor into a plurality of chambers, i.e. 50 and 52; and an internally depending partition 54 from the spacer 26 further divides the servomotor into chambers S6 and 58 between the movable walls 20 and 22. The movable walls 20 and 22 are formed of a similar hard plastic material and are united by a simple screw thread arrangement as at 60 to `move in unison inside the servomotor 10. As seen, the lwall 20 is provided with an axial opening or fluid passageway 62 opened to chamber 50 and by means of a radial passage 64 to chamber 56 behind the partition 54. Within the iaxiall passage 62 there is placed a force transmitting rod 66 which is provided with a reaction plate 68 arranged to hold a reaction disc 70 against a shoulder 72 adjacent the threaded end of the tubular projection about the axial passage 62. As seen, the shoulder 72 is provided with a central opening 74 into which the disc 70 is extruded by force applied on the rod 66 to oppose :movement of the walls 20 and 22. This opening 74 is appropriately sized to provide a proportional reaction of the force on the rod 66 to a valve operating control rod 76 by way of a valve plunger 78 having an end 80 slidably .received within the opening 74. The end 80 and in fact the valve plunger 78 is biased by means of a return spring 82 that is compressed between the tubular projection of wall 20 and a radial flange 84 of the plunge-r 78 and a depending shoulder 86 of the movable wall 22, so as to be normally spaced from the reaction disc 70. Behind the valve plunger 78 and rwithin a tubular portion 88 of the movable wall 22 extending rearwardly of the portion 14 of the servomotor 10 there is mounted a flexible poppet 90 held to the tubular portion 88 by a sealing washer92 arranged to bias ian outer thickened portion 94 of the exi-ble poppet 90 to the tubular portion 88. In addition, the exible poppet 90 is provided with an annular washer 96 immediately behind a forward face of the poppet 90 on which a spring 98 bears, which spring is compressed between ia flange 100 of the control rod 76 and the washer 96.

As seen, the tubular portion surrounding the passage 62 of the movable wall 20 and the tubular portion 88 are sealingly and bearingly supported by the partition 54 and the rear housing portion 14, respectively, as by means of bearing seals 102 and 104, and the push rod 66 is reciprocably supported Iand sealed by means of a seal (not shown) in the forward portion 12 of the servomotor housing. Furthermore, the movable walls 20 and 22 are biased to have a bulbous portion 108 on the rear face of diaphragm 38 4abutting a radially interned portion of the rear shell 14 by means of a conical spring 110 within the chamber 50, so that upon release of the control rod 76 the spring 110 will return the movable walls to the inoperative rearward position shown in FIGURE 1.

In operation, a vacuum supply, as from the manifold of a vehicle engine, is supplied by means of a check valve 112 in the front portion 12 of the servomotor housing to the chamber 50 and directed by means of passages 62 and 64 to chamber 56 wherefrom it is directed through an angular passage 114 in the movable wall 22 to valve cavity 116 around the outside of the exible poppet 90 As seen in FIGURE 1 in the released condition, the plunger 78 is abutting the face of the fiexible poppet 90 and holding the flexible poppet 90 off of a seat 122 formed on the rear face of the depending shoulder 86 of the movable wall 22 so that the vacuum created in the passage 114 will be directed in the released position about the valve plunger and poppet to a radial passage 124 leading from the movable wall valve chamber to chamber 52 of the servomotor 10. Vacuum i-n chamber 52 is then directed about the bulbous stops 108 on the diaphragm 38 through the slots in the diaphragm retainer to a space 126 about spacer 26 and therefrom through a radial passage 128 into -chamber 58. As an operator of the servomotor appplies force to the control rod 76, he moves the plunger 78 forwardly to abut the end 80 upon the disc 70 and seat the exible poppet 90 upon the valve seat 122 and remove the plunger 78 from the face of the poppet 90 so that atmosphere passing through filters 130 about the control r-od 76 will enter the radial passage 124 to chamber 52 and by passages 126 and 128 to chamber 58 so that a pressure differential is created across the movable walls 20 and 22 to move these walls forwardly and compress spring 110 thereby projecting force transmitting rod 66 outwardly of the servomotor 10.

If in the event there is no' vacuum applied to the check valve 112, .a mechanical connection is provided after a certain amount of travel between the radial ange 84 and an annular collar 132 so that direct force application from rod 76 will move the walls 20 and 22 to project the force transmitting rod 66 from the servomotor 10.

It is to be understood that the present invention is susceptible of various modifications and adaptations other than herein described and shown and that it is only limited by the scope of the appended claims.

I claim:

1. A servomotor comprising:

a housing having two portions which are joined together with la spacer means arranged to sealingly hold a irst flexible member and a second flexible member, said spacer means including a depending partition having a central opening;

a front movable wall having Ian annular groove whose internal dimensi-on is greater than an opening diameter of said first exible member to provide an interference fit as said first flexible member is snap-fitted into said groove to join said front movable wall and said first flexible member on a forward side of said partition, said front movable wall including :an integral rearwardly projecting tubular member which is threaded at its rearmost point and a radial slot ahead of said threads, said rearwardly projecting tubular member being sealingly and slidably supported in the central opening of said partition and open by means of a centr-al passage to a first variable volume chamber ahead of said front movable wall to communicate rsame with an area Within said housing behind said partition by way of said radial slot;

a rear movable wa-ll having Ian annular groove whose ,internal dimension is greater than an opening diameter of said second exible member to provide an interference t as said second exible member is snap-fitted into said groove to join said rear movtable wall and said second flexible member in said area to create a second variable volume chamber and a third variable volume chamber ahead and behind said rear movable wall, respectively, said rear movable wall having a threaded bore on a front face thereof receiving said threaded, rearwardly projecting tubular member to join said front and rear movable walls, which bore is open to a valve cavity in said rear movable wall communicated by a substantially axial passage in said rear movable wall to said second variable volume chamber and a radial passage to said third va-riable volume chamber and by means of a tubular extension to the exterior of said housing;

a passage means in said housing for communicating said third variable volume chamber to a fourth variable volume chamber ahead of said partition behind said front movable wall; and

valve means in said valve cavity to suspend the front and rear movable walls in an equal pressure medium or to create a pressure differential of equal magnitude across each of said walls, said valve means having a lost motion connection with said walls to be mechanically connected to both said walls by abutting said tubular projection of said front Wall after being operated to create the pressure differential` 2. A servomotor according to claim 1 wherein said front movable wall and said second movable wall are characterized as being constructed of hard plastic.

3. A servomotor according to claim 1,wherein said rearwardly projecting tubular member includes an annular projection arranged to extend into said valve cavity t-o form an abutting surface for said means to provide mechanical movement of said front movable wall and said rear movable Wall when said pressure on said means is greater than the effect of :a pressure differential across said front and rear movable walls.

4. A servomotor according to claim 1 and further comprising a return spring operatively connecting said valve means in said valve cavity to said front and rear movable walls.

5. A servomotor according to claim 1 wherein one of said portions is provided with a central opening in which is mounted a bearing seal for sealingly and slidably supporting said tubular member of said rear movable wall.

References Cited by the Examiner UNITED STATES PATENTS 2,265,842 12/ 1941 Kellogg 92-97 3,096,689 7/1963 Kytta 92-48 3,103,855 9/1963 Hager et al 92h48 FOREIGN PATENTS 964,289 7/ 1964 Great Britain.

MARTIN P. SCHWADRON, Primary Examiners P. E. MASLOUSKY. Asssranr Examiner, 

1. A SERVOMOTOR COMPRISING: A HOUSING HAVING TWO PORTIONS WHICH ARE JOINED TOGETHERE WITH A SPACER MEANS ARRANGED TO SEALINGLY HOLD A FIRST FLEXIBLE MEMBER AND A SECOND FLEXIBLE MEMBER, SAID SPACER MEANS INCLUDING A DEPENDING PARTITION HAVING A CENTRAL OPENING; A FRONT MOVABLE WALL HAVING AN ANNULAR GROOVE WHOSE INTERNAL DIMENSION IS GREATE THAN AN OPENING DIAMETER OF SAID FIRST FLEXIBLE MEMBER TO PROVIDE AN INTERFERENCE FIT AS SAID FIRST FLEXIBLE MEMBER IS SNAP-FITTED INTO SAID GROOVE TO JOIN SAID FRONT MOVABLE WALL AND SAID FIRST FLEXIBLE MEMBER ON A FORWARD SIDE OF SAID PARTITION, SAID FRONT MOVABLE WALL INCLUDING AN INTEGRAL REARWARDLY PROJECTING TUBULAR MEMBER WHICH IS THREADED AT ITS REARMOST POINT AND A RADIAL SLOT AHEAD OF SAID THREADS, SAID REARWARDLY PROJECTING TUBULAR MEMBER BEING SEALINGLY AND SLIDABLY SUPPORTED IN THE CENTRAL OPENING OF SAID PARTITION AND OPEN BY MEANS OF A CENTRAL PASSAGE TO A FIRST VARIABLE VOLUME CHAMBER AHEAD OF SAID FRONT MOVABLE WALL TO COMMUNICATE SAME WITH AN AREA WITHIN SAID HOUSING BEHIND SAID PARTITION BY WAY OF SAID RADIAL SLOT; A REAR MOVABLE WALL HAVING AN ANNULR GROOVE WHOSE INTERNAL DIMENSION IS GREATER THAN AN OPENING DIAMETER OF SAID SECOND FLEXIBLE MEMBER TO PROVIDE AN INTERFERENCE FIT AS SAID SECOND FLEXIBLE MEMBER IS SNAP-FITTED INTO SAID GROOVE TO JOIN SAID REAR MOVABLE WALL AND SAID SECOND FLEXIBLE MEMBER IN SAID AREA TO CREATE A SECOND VARIABLE VOLUME CHAMBER AND A THIRD VARIABLE VOLUME CHAMBER AHEAD AND BEHIND SAID REAR MOVABLE WALL, RESPECTIVIVELY, SAID REAR MOVABLE WALL HAVING A THREADED BORE ON A FRONT FACE THEREOF RECEIVING SAID THREADED, REARWARDLY PROJECTING TUBULAR MEMBER TO JOIN SAID FRONT AND REAR MOVABLE WALLS, WHICH BORE IS OPEN TO A VALVE CAVITY IN SAID REAR MOVABLE WALL COMMUNICATED BY A SUBSTANTIALLY AXIAL PASSAGE IN SAID REAR MOVABLE WALL TO SAID SECOND VARIABLE VOLUME CHAMBER AND A RADIAL PASSAGE TO SAID THIRD VARIABLE VOLUME CHAMBER AND BY MEANS OF A TUBULAR EXTENSION TO THE EXTERIOR OF SAID HOUSING; A PASSAGE MEANS IN SAID HOUSING FOR COMMUNICATING SAID THIRD VARIABLE VOLUME CHAMBER TO A FOURTH VARIABLE VOLUME CHAMBER AHEAD OF SAID PARTITION BEHIND SAID FRONT MOVABLE WALL; AND VALVE MEANS IN SAID VALVE CAVITY TO SUSPEND THE FRONT AND REAR MOVABLE WALLS IN AN EQUAL PRESSURE MEDIUM OR TO CREATE A PRESSURE DIFFERENTIAL OF EQUAL MAGNITUDE ACROSS EACH OF SAID WALLS, SAID VALVE MEANS HAVING A LOST MOTION CONNECTION WITH SAID WALLS TO BE MECHANICALLY CONNECTED TO BOTH SAID WALLS BY ABUTTING SAID TUBULAR PROJECTION OF SAID FRONT WALL AFTER BEING OPERATED TO CREATE THE PRESSURE DIFFERENTIAL. 